Great work in the painting part, really likes the sharp contrast of colours, and the highlights. Now going to the feedback and shapes. I would suggest two ways of thinking about improving your shape design. One is external (silhouette, the abstract ) and second is internal (internal form indication , as done by shadow). But first, let's discuss what differentiates a " Good " design from a "Bad" design. What we calls a "Good" design is simply a design which very intensional with what it communicates. Regardless of subject, the shapes themselves communicates two things, 1. Emotion 2. Context of content. Bounding our discussion to 3 shapes, shapes as circles communicates intuitively suggests a softer, safer nature for subject and evokes the same emotion of safety in viewer, whereas a square communicates a much more reliable, strong nature from the subject. But a triangle or sharp corners would suggest a sharp , potentially dangerous and alarming subject. Just observe around, round as a ball "cute" puppy, or triangulate as a knief "scary" spiders , or tree trunk on which i could hit my head and would not break..... And so on , you get the idea. The second part "context of content" is more of related to the shape and what we assosiate certain subjects to, as are crosses to religion ( as used a lot in mihawk) , exposive cloths to modernism and cleverness ( as in nami ), even eagle to pride and chivalry trails, ... the list goes on and on for every shape we could connect to a particular idea . Theory ended, now what's the implication for your part ? You could apply this theory in the external silhouette of mihawk by choosing the silhouette shapes to be more rounded , more angular, or squarish. For oda's choice, he chose to make mihawk's silhouette shapes more squarish and reliable . Next, the same theory can also be applied for choosing the shapes we decide for shadow shapes. This time, oda chose to keep mihawk's internal shapes ( as beard and moustache) more triangular. Lastly, mihawk's whole design is filled with crosses , from sword to ship. Yiu may wish to exaggerate this even further by pushing some other shapes as well to be resembling to crosses , or maybe give him his Gospels and make a new personality altogether.